Racing connections are those people that own and work with a thoroughbred race horse. The owner(s), trainer, rider(s) and stable employees. In terms of handicapping a horse race, the trainer and jockey will be most significant, but it's important to understand the numerous complexities arising from this human interaction with a racehorse.
The trainer of a racehorse will be an elemental component to its development
The trainer of a thoroughbred racehorse will be an elemental component to its future development and running ability. The trainer will observe the race horse entrusted to be under his care, provide an optimum diet; and develop an exercise routine with immediate and long term racing objectives in mind.
The job of the trainer is to prepare a race horse for competition and then to enter the horse in a race at a certain distance, within a certain class level; where it can win or be competitive.
Therefore since trainers usually have full control over which race a horse is entered in, they will often maneuver a horse up or down in Class for strategic reasons, in search of a group it can beat.
Sometimes the racing secretary does an awesome job in sending a group of equally matched competitors to the post. In such races, riders will often "use up" their mounts jockeying for position; and in such races, time and time again, a clever rider will make all the difference in the world.
Mind you, no trainer or jockey can win, a horse will win the horse race, and any horse that is not sound or outclassed will not win today. That said, there are certain clues to lookout for which can be indicators of a live horse ready to win.
The positive jockey switch, to a leading rider, especially when combined with a jump or drop in Class. The leading rider whom all of a sudden shows up on a mount for an obscure barn.
The leading rider who has his choice of mounts in a race, especially when getting off a horse which he rode to victory in its last race, in favor of another.